In this study, in a genetic screen in the vinegar fly, Drosophila melanogaster, for genes that cooperate with a mutation in the cell polarity (shape) regulator, scribbled (scrib), we identify a novel cooperative oncogene, abrupt. Expression of abrupt in scrib mutant tissue in the developing eye/antennal epithelium results in overgrown invasive tumours. This evidence concerns the gene SCRIB and neoplasm.